Research On Low Frequency Ultrasonic Transducer For Neuromodulation

The emergence of neuromodulation provides a new treatment method for neurological diseases,and with the development of neuromodulation technology,there are many new neuromodulation methods emerged.Common non-invasive neuromodulation methods mainly include transcranial direct current stimulation and transcranial magnetic stimulation,but both have the disadvantages of poor resolution and shallow penetration depth,so researchers are increasingly paying attention to the possibility of ultrasound as a neuromodulation tool.In order to promote the development of ultrasound neuromodulation,the paper was based on the finite element simulation software PZFlex to design and simulate the performance of the ultrasonic transducer for neuromodulation,and prepare the device to study its biological application.The main research contents and results are as follows:(1)Because the existing ultrasonic transducers for neuromodulation have the problem of large device size and poor resolution,the finite element simulation software PZFlex was used in the paper to design and simulate half concave focused ultrasonic transducers with different dimpling curvature.Besides,a plane transducer was simulated as a control group.The simulation results show that the half concave structure can improve the lateral resolution of the low-frequency ultrasonic transducer,and the smaller the dimpling curvature is,the more significant the resolution improved.Among them,the half concave focused ultrasonic transducer with a dimpling curvature of 5 mm has a-3 dB lateral resolution of only 1.67 mm,which has a better resolution than most ultrasonic transducers for neuromodulation.In addition,the half concave structure makes the acoustic pressure at the focal point of the ultrasonic transducer increased slightly.Under the condition that the excitation conditions remain unchanged,this structure provides a new method to increase the intensity of the acoustic field.(2)Prepare a half concave focused ultrasonic transducer and a plane ultrasonic transducer as a control group according to the simulation results.Due to the limitation of the process conditions,two half concave focused ultrasonic transducers with a dimpling curvature of 5 mm and 7.5 mm were prepared.Subsequently,a multifunctional ultrasonic test platform built in the laboratory was used to characterize the emission acoustic field of ultrasonic transducers with different structures at its thickness resonance frequency(1 MHz).The experimental results are basically consistent with the simulation results.Compared with the plane ultrasonic transducer,the-3 dB lateral resolution(1.45 mm)of the half concave focused ultrasonic transducer with the dimpling curvature of 5 mm is approximately half of that of the plane ultrasonic transducer(2.65 mm),further indicating that the half concave focused ultrasonic transducer is expected to achieve more accurate neuromodulation effects.(3)The emission acoustic field of half concave focused ultrasonic transducer and plane ultrasonic transducer at 400 kHz was simulated and characterized,and simulation models with skull were created to further study the neuromodulation ability of the half concave focused ultrasonic transducer.Three ultrasonic transducers with different structures were used to neuromodulate the motor cortex of the mouse brain and the motor response was monitored.The results show that the half concave focused ultrasonic transducer has a higher neuromodulation success rate than that of the plane ultrasonic transducer.The success rate of the plane ultrasonic transducer,the half concave focused ultrasonic transducer with a dimpling curvature of 7.5 mm and the half concave focused ultrasonic transducer with a dimpling curvature of 5 mm are(32±10)%,(65±8)%and(84±7)%respectively.